I have a piece that is about a year old of platinum silicone. I have to take it in and re-glue it, but as I feared, using regular 2-part plat silicone isn't adhering. Smooth-on wants to sell me sil-poxy but it's really expensive.
Clean the surface really well, with heptane, for example, after that use acetone to remove the oil feeling of the heptane and use silicone caulking. Use preferably acetic one, not the neutral. The acetic(smell like vinegar) are stronger and more flexible.